A composite color video signal includes horizontal synchronizing signals, a burst signal superimposed onto the pedestal level at the back porch of the horizontal synchronizing signal and a video information signal. The video information signal comprises a chrominance subcarrier having different phases with the amplitude-modulated chrominance information. The composite color video signal includes both luminance and chrominance information.
To encode RGB signals into a composite video signal which is compatible with the acceptable standards, the subcarrier signal should be included. This subcarrier signal is used as a reference during the chroma decoding process. This subcarrier reference signal must be inserted at the proper place in the composite video signal. The subcarrier reference signal must also have the proper duration. The position and the width of the subcarrier reference signal pulse is critical in order for the receivers to correctly decode the chroma signals.
Burst gate pulse generator circuits of the prior art have used external components to generate the precision timing signals necessary to generate a burst gate pulse. External components are required because the absolute accuracy of devices within an integrated circuit environment is quite poor. However, the relative accuracy of devices within such a circuit is very good. In fact, the relative value of a pair of matched identical resistors will typically deviate by less than one percent. External components are used in such burst gate pulse generator circuits because they may be selected for high absolute accuracy, thereby providing means to generate the high absolute accuracy timing signals necessary to generate an accurate burst gate pulse. External components are undesirable because they add costs to a system, take up extra space around a circuit within the system and require a dedicated pin on the integrated circuit to which they are coupled, therefore mandating that the integrated circuit is bigger than it otherwise would have to be. What is needed is a burst gate pulse generator circuit which does not require external components to generate the timing signals and a burst gate pulse.